So....two questions that are largely unrelated.
1. About Ren ancestor worship...from what i gatherd from storms of Yizaho, the ren seem to beliefe, that continued sacrifice is required to keep their ancestors out of hell. Is that true or am i mireading that? And would it mean that, if ren abandond the pattern, they risk all their ancestors loosing their safety in the grave?
2. extending dominion. The book says, that when the regional scope of a change is expanded,only the difference between the original change and the new scope needs to be paid. Since the scope of changes are not linear, my question is at what point an "upgrade" should have to be paid by linearly expanding godbound. Case in point, if you godbounds rule a kingdome, say patria, give it a bunch changes and institutions, and then swallow Raktia and Vissio into their new theocrat empires, what, if anything, should they pay to extend their changes to the new provinces. Their area has just doubeld in size, but is still far from the size of arcem.
2: the GM has here full control, and there are more factors involved (like Mundus wards or opposing changes). A region base cost is 4 modified by the opposition and multiplied by the possibility factor, and the result is compared to your invested Dominion. If there is no opposition and it is a possible change [4 - (4 x 1) = 0 extra Dominion] if there is, it can get expensive...
For 1, that does seem a possibility, if the new faith doesn’t incorporate the ancestor worship, or if the new faith involved doesn’t figure out how to preserve all the resting souls.
+Anton .Shami IIRC, there is no specific determination over whether it works or not. It's left up to the GM to determine which case is more interesting. Assuming it works creates a unique exception in the world which demands explanation and opens up plot ideas, while assuming it doesn't work implies a culture waiting to have its core beliefs and society shaken up and opens up plot ideas.